1. Field of the Invention
The present invention relates to an axial turbine, such as a steam turbine or a gas turbine, and specifically, to an axial turbine for low pressure (i.e., a low-pressure turbine).
2. Description of the Related Art
The axial turbine increases the speed of a working fluid by allowing it to pass through stationary blades, deflects the working fluid in the rotational direction of a turbine rotor, and rotates the turbine by providing kinetic energy to moving blades by a flow having a velocity component in the rotational direction. In order to induce such a flow of the working fluid for driving the turbine rotor, the height of the outlet flow path of a turbine stage, measured in the radial direction of the turbine rotor is made higher than the height of the inlet flow path of the turbine stage, in conformance to the fact that the inlet of the turbine stage is higher in pressure than the outlet thereof. As a result, generally, in a stationary blade annular plane outer peripheral portion in each stage, the flow path height monotonously increases from the inlet toward the outlet of the stage. In other words, the radial height of the outlet of stationary blade becomes higher than the radial height of the inlet thereof (refer to JP, A 2003-27901 for example).